BackPlane Buses

This is a subdivision of the Interface bus listing. Buses designed to operate over backplanes [or Mother Boards] are listed here. A bus which operates over a backplane is used to communicate between two or more CCAs via an interconnecting PCB [a back-plane or MotherBoard]. Normally card busses operate over a passive backplane. A brief description of each bus type is listed below, with a more detailed description on the individual page provided by the link. In addition all of the pages provide links to component or equipment manufacturers. All sub-VME bus types which operate over P0 or P2 connectors are listed with descriptions on the VME (P2) Add on Buses page and not on this page.



AdvancedTCA Bus {Advanced Telcom Computing Architecture [ATCA] Backplane bus used in central office grade equipment. A maximum of 14 CCA's will be supported in one chassis. CCA; Circuit Card Assembly, Telcom; telecommunication}

AdvancedTCA Express {The PCIe version of ATCA}

AGP Bus {Accelerated Graphics Port [AGP], PC Mother Board Local Bus. The AGP bus is a Chip-to-Chip bus operating between cards plugged into a PC backplane operating at a speed of 2.1GB/s. Normally on PC Mother Boards there is only one AGP expansion slot used as a video card slot.}

AT96; {The AT96 bus runs over either a AT96 backplane, or a cable between two AT96 boards. This bus is similar to the AT bus used in IBM compatible computers. AT96 is electrically compatible with the IBM AT bus. This bus is OBSOLETE.)

AXIe {AdvancedTCA Extensions for Instrumentation and Test. Same principle as VXI, PXI and LXI.}

COM Express; [Computer-on-Modules Express, COMe]. Embedded computer board standard controlled by PICMG. COM Express uses the ETX form factor [see below] which was originally developed by Kontron. COM Express supports PCI Express, Serial ATA, Serial DVO, and LVDS. COMe modules are produced in the basic form factor of 125mm x 95mm, or in the Extended form factor of 155mm x 110mm. COM Express is the PCI Express version of ETX; (Embedded Technology eXtended) with a form factor of: 95mm x 111.6mm (5.75 x 8 inches).

Compact PCI Bus {cPCI uses the PCI bus in an embedded form factor. The difference between cPCI and the PCI bus lay with the form factor, the board size and connectors are different.}

cPCI Express {Also called CPCIe. PCI Express [PCIe] on a 3U x 160mm form factor or 6U form factor in a Compact PCI [cPCI] environment. The PCI Express 16x and 8x lanes are routed on the P1 and P2 connectors, all other connectors are free for other I/O. See the CompactPCI, or PCI Express listing for additional information.}

CompactTCA {offers fabric support similar to AdvancedTCA but at a reduced bandwidth in a 6U "CompactPCI compatible" form factor. Refer to AdvancedTCA, or Compact PCI listed above.}

CT Bus {Computer Telephony [CT] Backplane Bus description, Information and Specification Links. Another Telecommunications [Telcom] bus which may be implemented on either a PCI or cPCI card as a sub bus}

EBX {The Embedded Board eXpandable is an Embedded computer board standard now supported by PICMG. The EBX form factor is 8.00" x 5.75", and may be used as a PC104 platform. EBX is not a bus standard, but a board standard, or more correctly an embedded SBC [Single Board Computer]. EBX also supports a PCMCIA slot: PC Card standard.}

Embedded PCI-X Specification {[ePCI-X], The PICMG 1.2 specification defines the mechanical and electrical interface to support a standard form factor PCI computer system with either two PCI/PCI-X busses or a single PCI/PCI-X bus. The document also defines the electrical and mechanical connections for a single board computer and backplane. This is an upgrade to the PCI-ISA specification. PCI-X capabilities are added to the PCI bus and the ISA bus is replaced by a second PCI-X bus, on the PCI-ISA backplane. The board retains the same mechanical dimensions as PCI-ISA but the components move to the PCI side and the slot occupies a PCI position on a backplane. Also refer to the PCI-ISA listing, or the PCI listing}

ETX (Embedded Technology eXtended) with a form factor of: 95mm x 111.6mm (5.75 x 8 inches). Is an Embedded computer board standard supported by PICMG. ETX is a board standard, not a bus standard

EPIC (Embedded Platform for Industrial Computing) with a form factor of: 4.5" x 6.5". EPIC is smaller then the EBX standard. EPIC is an embedded SBC format which also supports PC/104 modules.

FastBus {IEEE Std 960-1993 Defines the Mechanical, Electrical, and Protocol layers. FastBus used a 32 bit address and data bus. A standard rack-mountable crate had 26 slots. The backplane used asynchronous ECL signals. This bus is out-dated but still in operation ~ not recommended for new designs.}

FireWire Bus {IEEE 1394 Bus may be used as a backplane interface, but is better known as a serial cable bus. The backplane bus version uses two single ended signals and operates at either 12.5 [TTL], 25 [TTL], or 50Mbps [using BTL or ECL].}

Futurebus {Futurebus Backplane Description, which is not widely used. Futurebus+ is also described. A 256 bit wide bus by 100MHz. The bus width is uncommon.}

HyperTransport Bus (Backplane Bus Description. HyperTransport is another point-to-point differential bus using LVDS. The HyperTransport Bus is used in servers.)

InfiniBand bus (Bus Description, and IC Manufacturers. InfiniBand uses LVDS devices as an electrical interface)

IndustrialPCI {What seems to be some european rendition of cPCI. The standard dates from 1995 to 1998. The bus uses a 5-slot passive backplane, with one system slot, and operates with a 32-bit/64-bit bus using either 5 volt or 3.3 volt systems. The specification uses Eurocard formats and DIN Connectors. It does not appear that this standard gained wide approval, perhaps because of cPCI}

Industrial PCI Express {[IPCI-E], PICMG 1.3 adds PCI Express to the PCI-ISA Passive Backplane Specification. The PCI-ISA bus is described below.}

LVDS Bus {LVDS/M-LVDS Wiring Standard description, and Information. LVDS is used as the electrical interface on many other interface buses}

MicroTCA {defines a backplane architecture designed to support AdvancedMC (AMC) modules}

Multibus I/II {IEEE-1296 had a 32 bit bus which ran at 80MBps, the card sizes are 3U x 220mm, and 6U x 220mm. This bus is out-dated but still in operation ~ The Multibus interface is not recommended for new designs.}

PC Bus {ISA/XT/EISA; early IBM compatible Personal Computer Buses. These PC busses are not recommended for new designs, and were all replaced by the PCI bus}

PCI Bus {The Peripheral Component Interface 'PCI' [Parallel] Bus was originally developed as a local bus expansion for the PC. The first version of the PCI bus ran at 33MHz with a 32 bit bus (133MBps), the current version runs at 66MHz with a 64 bit bus. The PCI bus operates either synchronously or asynchronously with the "mother Board bus rate: The page contains the PCI connector Pin-Outs. The PCI bus is also used on/with many other interface bus standards.}

PCI-X Bus {The Peripheral Component Interface [PCI-X] addendum is an enhancement to the current 64 bit 66MHz PCI bus specification. The minimum clock speed for PCI-X is 66MHz [PCI-X 66]. Additional bus speeds include: PCI-X 133, PCI-X 266 and PCI-X 533 providing up to 4.3GBps [PCI-X 1066 in the works]. PCI-X is backwards compatible with PCI}

PCI Express Bus {Serial PCI Bus uses two low-voltage differential LVDS pairs, at 2.5Gb/s in each direction. Using 8B/10B encoding, and Supporting 1x, 2x, 4x, 8x, 12x, 16x, 32x bus widths. Set to replace the Parallel PCI bus; PCI, and PCI-X}

PCI Express ASI { [Advanced Switching Interconnect]. An extension to the Serial PCI Express Bus uses the identical physical layer [two low-voltage differential LVDS pairs, at 2.5Gb/s in each direction], and Data Link Layer. ASI is designed to support multiple hosts and multiple address spaces with no restrictions on fabric topologies. The difference is at the Transaction layer}

PCI-ISA {A passive backplane which moves all active devices off the motherboard and onto a single card. The controller card used in the system has fingers [edge connectors] for both PCI and the ISA bus, the Mother Board only connectors. This allows additional cards to be added to the mother board which use either the ISA or PCI buses. Because only connectors reside on the mother board, repair time is increased, and down time is decreased. The standard is PICMG-xx [1995]. The specification is used in embedded or industrial computer systems. Also refer to the Embedded PCI-X listing for an up-grade path, replacing the ISA slots with PCI-X}


PC-104 Bus {PC/104 Bus is used as an embedded PC bus, combining the IBM compatible ISA buses; XT, and AT buses into a different form factor [Card size]. The boards stack on top of each other.}

PC104-Plus Bus {Adds the PCI bus [and a new connector] to the PC104 bus in the same PC104 form factor [board size]. Listed on the PC/104 page.}

PCI-104 Bus {Removes the IBM XT, and AT buses from the PC/104, and PC/104-Plus boards, but keeps the same PC104 form factor [board size] leaving only the 33MHz PCI bus.}

PCI/104-Express Bus {Combines the PCI interface and PCIe interface, but keeps the same PC104 form factor [board size], The older XT/AT buses are not included.}

PCIe/104 Bus {A PC/104 board which only includes a PCIe interface, no other buses are included.}

PXI {PCI eXtensions for Instrumentation [PXI] defines cPCI for Instrumentation adding additional enhancements, with the same form factor as cPCI.}

PXI Express {PCI eXtensions for Instrumentation Express [PXIe] defines cPCIe for Instrumentation adding additional enhancements, with the same form factor as cPCIe.}

Q-Bus {A backplane bus used on the now obsolete PDP and MicroVAX computer systems.}

RapidIO {Uses LVDS for high-performance embedded applications such as networking, storage, multimedia, and signal processing to 10Gbps}

SHB Express {System Host Board [PCI Express], also called SHBe. The mother board supports a removable System Host Board [SHB] in addition to other I/O boards. The SHB is produced as a full length or short form factor. Both board types support x16 and x8 PCI Express lanes. SHB Express is used as an industrial embedded computer system}

StackableUSB {Standard USB 2.0 interface that uses USB connectors and board-stackble, with no USB cables.}

STD32 {8/16/32 bit TTL data bus running at 32MBps. The STD bus [1978] and STD32 bus [1989] cards may not be interchanged, and are incompatible. This bus is out-dated but still in operation ~ not recommended for new designs.}

STEbus {STandard Eurocard, IEEE1000; 8 bit Data bus using TTL logic, with 20 Address lines. The STEbus came in either a 3U or 6U board format. A 1980 era bus, OBSOLETE}

SwitchedFabric Buses {Definition of different buses, Links, and Specifications}

VERSAbus {Backplane bus defined by Motorola Corporation in 1979 for its 68000 microprocessor. This bus is OBSOLETE. In limited cases the term VERSAbus may be used to refer to the VME Bus, as in VERSAmodule Eurocard Bus. VERSAbus was the basis for the electrical standard for the VME bus, and the Eurocard format was the basis for the mechanical standard for VME. The VERSAbus standard used card edge connectors [fingers], while the VME bus uses DIN connectors.}

VME Bus {VMEbus description, P1/P2 connector pin-out, IC, Connector and device Manufacturing Links. VME uses 8-bit to 62-bit data transfers, and 23-bit to 40-bit addresses. The current VMEbus throughput is 80MBps for VME64x, which has been up-graded from a 40MBps throughput in the previous standard. Also there are a number of other buses which run over the uncommitted P2 and P0 connectors which may enhance the throughput. Other names which refer to the VMEbus [but are vary uncommon] include; VERSAmodule European, VERSAmodule Europe, VERSAbus-E, and VERSAmodule Eurocard}

VME add-on Bus(s) {SkyChannel - RACEWay - Infiniband - P2CI - FPDP - Autobahn interface buses}

VPX {The new generation in VME Buses}

VXI Bus {VXIbus description, P1/P2 connector pin-out, Timing, IC/Connector manufacturers. VME for Instrumentation}

XTX (eXtended Technology ETX) with a form factor of: 95mm x 111.6mm (5.75 x 8 inches). XTX is an Embedded computer board standard, an extension of the ETX board. XTX is a board standard, not a bus standard. XTX removes the ISA interface on the X2 connector [used on ETX] and replaces it with PCIe, SATA, USB .... interfaces

Additional BackPlane Busses
{NIM Bus, and CAMAC, or a few other interface not yet listed here.}

All of the different Backplane interface bus descriptions or links to electronic bus pages listed above deal with layer 1 [Physical, Electrical and Mechanical Layer] of the OSI protocol stack. Many electronic bus pages also reference layer 2; the Data Link Layer [which provide bit/byte stuffing, checksum, Protocols..]. In addition, all of the page links listed above provide links to devices related to that particular bus, which include IC manufacturers, Connector manufacturers, Bus Termination manufacturers, cable manufacturers, and electronic equipment manufacturers, Standards/Specifications and so on... The extent of the description provided for any particular electronic bus varies widely from page to page depending on the bus. In only a few occasions is a particular bus listed as Obsolete; however, there may be many buses listed, if not obsolete, which should not be used for new designs. Some Busses have a number of revisions; check for the latest revision to insure the bus is still in operation.

PC motherboard

Distributor rolodex Electronic Components Electronic Equipment EDA CDROM Software Engineering Standards, BOB card Cabled Computer Bus Electronic Engineering Design Table Conversion DB9-to-DB25.
DistributorsComponents Equipment Software Standards Buses Design Reference

Modified 7/15/2015
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